The Actor-Mixer Hierarchy groups and organizes all the sound and motion assets in your project. At the base of this hierarchy are all your individual sound and motion objects. You can define the properties and behaviors of these individual objects, but you can also take these objects and group them together so that you can define their properties and behaviors as a unit. To accommodate the complex nature of audio within a game, different types of objects can exist within the Wwise project hierarchy. Each object type has a set of properties, such as volume, pitch, and positioning, and a set of unique behaviors, such as random or sequence playback. By using different object types to group sounds within your project hierarchy, you can define specific playback behaviors of a group of sounds within the game. You can also define these properties and behaviors at different levels within the hierarchy to obtain different results.

Since motion is generally tied to audio in a game, Wwise uses the same principles and workflow for generating motion. This means that you can organize the motion assets for your game into hierarchies, and assign properties and behaviors in the same way as your audio assets.

You can use a combination of the following object types to group your assets and build a structure for your project:

The various voice and sfx assets in your game are represented in Wwise by special audio structures called sound objects. These sound objects contain sources that are linked to the original audio file.

The audio source is a separate layer between the imported audio file and the sound object. By adding an abstraction layer, you can have multiple sources and audio files all contained within the same sound object.

This not only makes it easy to test different conversion settings but also allows you to efficiently manage multi-language development.

Note: Wwise uses a similar method to manage the music and motion assets in your project.

Sound objects not only support audio sources, but they also support plug-in sources.

Wwise ships with a variety of source plug-ins, including a tone generator, silence, and audio input plug-in. In addition to being immediately useful in your production pipeline, the main purpose of these is to be used in conjunction with provided source code as a reference for programmers who are interested in building their own. With the creation and management of audio structures being done in Wwise by the sound designer, programmers are now free to develop a variety of source plug-ins, pushing the envelope in audio design and enhancing the overall experience of the game.

These sound objects can be grouped together to create a hierarchical project structure. Audio properties and behaviors can be applied at different levels in the hierarchy to give you the control and flexibility you need to build a realistic and immersive game experience.

Containers are used to group the sound objects within your project. They are mainly used to play a group of objects according to a certain behavior, such as Random, Sequence, Switch, and so on. For example, you can group all the gun shot firing sounds into a Random Container so that a different sound will be played each time the gun is fired in game.

All these audio structures are routed through a hierarchy of busses where additional properties and effects can be applied at a global level.

The following table shows you which tasks related to audio structures are the responsibility of the sound designer and which ones are the responsibility of the programmer:

Wwise offers you great flexibility when it comes to creating the interactive music for your project. There is an almost infinite number of ways to assemble interactive music objects into a game score. However, following some kind of consistent structure can make your workflow more efficient.

Two of the basic structures that can be applied to interactive music projects are as follows:

Typically, you'll use a combination of both these structures to make efficient use of the resources you have available for your project. A good structure lets you show off your music, and make the most of your console resources.

On top of the Actor-Mixer and Interactive Music hierarchies sits the Master-Mixer hierarchy. The Master-Mixer hierarchy is a separate hierarchical structure of busses that allows you to re-group and mix the many different sound, music, and motion structures within your project and prepare them for output. The Master-Mixer hierarchy is divided into two sections: one for sound and music, and one for motion. Each section consists of a top-level “Master Bus” and any number of child busses below it.

You can choose to route sound, music, and motion structures through these busses using the main categories within your game. For example, you may want to group all the different audio structures into the following four categories:

These busses not only create the final level of control for the sound, music, and motion structures within your project but they can also determine which sounds are affected by environmental effects such as Reverb. Because they sit on top of your project hierarchy, you can use them to create the final mix for your game. Depending on the platform, certain effects, including environmental effects, may also be applied to the busses to create that immersive experience that your game requires.

You can also use the Audio Bus structure to troubleshoot problems within your game. For example, you may want to solo specific voice, ambient sounds, or sound effects busses, to identify specific sounds or music.

The following illustration shows an example of a Master Audio Bus hierarchy that uses two preliminary busses to separate the environmental versus the non-environmental sounds and then uses several other audio busses to regroup some of the sound structures in the Actor-Mixer hierarchy and some of the music structures in the Interactive Music hierarchy.

	Note
	A similar hierarchy can be created at the same level under the Master Motion Bus for all the motion structures in your project.